The three specific aims of this project continue to focus on the role of two maternal environmental factors (diet and physical activity) in prenatal growth regulation and their indirect effects, if any on postnatal growth and development. The project uses a prospective, randomized design to evaluate the effects of maternal diet and activity on maternal blood glucose levels, feto-placental growth, and post-natal growth and development. Parallel mechanistic studies will also be carried out using a prospective, randomized cross-over design. The basic hypothesis to be tested is that diet and activity during pregnancy modulate many aspects of the growth process through their effects on multiple maternal metabolic and cardiovascular parameters. The specific maternal parameters which will be evaluated include: glucose, insulin, glycolated hemoglobin, TNF-alpha, and leptin levels, metabolizable energy intake, weight gain and fat deposition, resting metabolic rate, glucose oxidative and non-oxidative disposal, and insulin sensitivity. Placental growth and functional capacity will also be evaluated as well as neonatal morphometrics and postnatal growth, metabolism and neurodevelopment. The techniques used include: tight control of the subject's diet and activity, diet and exercise tolerance tests, ultrasound, indirect calorimetry, stable isotope infusion, the hyperinsulinemic-euglycemic clamp, and standard gross and microscopic morphometry. The significance of the project is that it will define the effects of diet and physical activity during pregnancy on outcome and identify some of the underlying mechanisms responsible for these effects.